Pulsed laser photolysis–long path laser absorption kinetics study of the reaction of methylperoxy radicals with NO2

The technique of pulsed laser photolysis–long path laser absorption is employed to study the kinetics of the reaction CH3O2+NO2+N2 k1→CH3O2NO2+N2 over the temperature range 253–353 K. CH3O2 is prepared by 193 nm (ArF) laser photolysis of azomethane in the presence of O2. The temporal profile of [CH3O2] is followed by measurement of the time resolved attenuation of a frequency doubled argon ion laser beam (257 nm). A path length of 860 cm is employed to obtain initial absorptions of (typically) 4%, corresponding to a CH3O2 concentration of 2×1013 cm−3. At all temperatures, k1 is found to increase monotonically but nonlinearly with increasing N2 pressure (76–722 Torr) indicating that Reaction (1) proceeds predominantly via an addition mechanism and that the reaction is in the falloff region between second and third order kinetics. The measured values of k1 are compared with results of previous investigations and their atmospheric implications discussed.